Decompensated severe hypothyroidism with altered mental status and hypothermia; mortality 30-50%.
Also known as: myxedema coma, myxedema crisis, hypothyroid coma, decompensated hypothyroidism
Overview
End-stage decompensated hypothyroidism characterized by altered mental status, hypothermia, and multisystem organ failure. Despite the name, frank coma is uncommon — the typical patient is obtunded, not unresponsive.
Epidemiology
Rare (estimated 0.22 per million per year), but mortality remains 30-50% even with treatment. Predominantly affects elderly women with long-standing untreated or undertreated hypothyroidism, typically precipitated in winter.
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Question 1EndocrineMedium
In January, a 74-year-old woman is brought to the emergency department after her daughter found her difficult to rouse. She has a history of hypothyroidism but stopped her levothyroxine several months ago. Temperature is 34.1°C (93.4°F), heart rate 48/min, blood pressure 96/70 mm Hg, and respirations 8/min. She is obtunded with non-pitting facial puffiness, an enlarged tongue, dry coarse skin, and a thyroidectomy scar. Deep tendon reflexes show delayed relaxation. Labs show sodium 122 mEq/L and glucose 54 mg/dL. Which of the following is the most likely diagnosis?
AHepatic stupor
BAdrenal crisis
CMyxedema coma
DDrug toxicity
Reveal answer & full explanation
Correct answer: C — Myxedema coma
AHepatic stupor
BAdrenal crisis
CMyxedema coma✓
DDrug toxicity
Why Myxedema coma is correct
This is end-stage decompensated hypothyroidism: an elderly woman in winter, obtunded after stopping levothyroxine, with the diagnostic triad of altered mental status, hypothermia (34.1°C), and a precipitant (cold exposure plus medication nonadherence).
The exam is classic for severe hypothyroidism — non-pitting myxedematous facial puffiness, macroglossia, dry coarse skin, a thyroidectomy scar, and delayed (hung-up) deep tendon reflex relaxation.
The constellation of bradycardia, hypotension, hypoventilation, hyponatremia (impaired free-water excretion), and hypoglycemia reflects the global drop in metabolic rate, cardiac output, and respiratory drive that defines the syndrome.
Management priority: stress-dose hydrocortisone FIRST (coexisting adrenal insufficiency is common), THEN IV levothyroxine, passive rewarming only, and an aggressive search for the precipitant.
Why the others are wrong
Adrenal crisis also causes hypotension, hyponatremia, and hypoglycemia and frequently coexists with myxedema coma, but it produces hyperpigmentation and shock rather than the profound hypothermia, bradycardia, and classic myxedematous facial and skin findings seen here.
Hepatic stupor (hepatic encephalopathy) is altered mentation from liver failure, but it features asterixis and elevated ammonia with stigmata of chronic liver disease, not hypothermia, macroglossia, myxedematous skin, or a thyroidectomy scar.
Drug toxicity from a sedative or opioid depresses consciousness and respiration but would not explain the hypothermia with myxedematous facies, macroglossia, delayed-relaxation reflexes, thyroidectomy scar, and hyponatremia in a patient off her thyroid medication.
Question 2EndocrineMedium
In January, a 74-year-old woman is brought to the ED after her daughter found her obtunded at home. She stopped taking her levothyroxine several months ago. Temperature is 34.1°C (93.4°F), heart rate 46/min, blood pressure 88/54 mm Hg, and respirations 8/min. She has periorbital edema, macroglossia, a thyroidectomy scar, and delayed relaxation of the deep tendon reflexes. Labs show sodium 124 mEq/L, glucose 58 mg/dL, markedly elevated TSH, and low free T4. She is intubated and started on warmed blankets and IV normal saline with dextrose. Which of the following is the most appropriate initial pharmacologic management?
AIV levothyroxine without any glucocorticoid
BIV levothyroxine, then IV hydrocortisone
CIV liothyronine, then IV hydrocortisone
DIV hydrocortisone, then IV levothyroxine
Reveal answer & full explanation
Correct answer: D — IV hydrocortisone, then IV levothyroxine
AIV levothyroxine without any glucocorticoid
BIV levothyroxine, then IV hydrocortisone
CIV liothyronine, then IV hydrocortisone
DIV hydrocortisone, then IV levothyroxine✓
Why IV hydrocortisone, then IV levothyroxine is correct
This patient has myxedema coma: decompensated hypothyroidism with altered mental status, hypothermia, bradycardia, hypotension, hyponatremia, and hypoglycemia precipitated by stopping levothyroxine in winter.
Stress-dose glucocorticoid (hydrocortisone 100 mg IV q8h) is given FIRST and continued until coexisting adrenal insufficiency is excluded. Concurrent adrenal insufficiency is common, and giving thyroid hormone before steroids increases metabolic demand and cortisol clearance, precipitating adrenal crisis.
After steroids are on board, thyroid hormone is replaced (levothyroxine 200-400 mcg IV load, then 50-100 mcg IV daily), alongside passive rewarming, cautious fluids, slow sodium correction, glucose, and treatment of any precipitant.
Why the others are wrong
IV levothyroxine, then IV hydrocortisone: correct drugs but wrong order; thyroid hormone before glucocorticoid can trigger adrenal crisis in the frequently coexisting adrenal insufficiency.
IV liothyronine, then IV hydrocortisone: levothyroxine (T4), not liothyronine (T3), is the primary agent; T3 is only sometimes added cautiously because of arrhythmia risk in elderly cardiac patients, and giving any thyroid hormone before the glucocorticoid still risks adrenal crisis.
IV levothyroxine without any glucocorticoid: omits the mandatory empiric stress-dose steroid, the central safety step in myxedema coma management.
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Long-standing hypothyroidism, often untreated or with poor adherence
Elderly female, winter months, cold exposure
Precipitants: infection (especially pneumonia, UTI, sepsis), MI, stroke, GI bleed, trauma, surgery
Sedative or opioid administration in undiagnosed hypothyroidism
Amiodarone, lithium, abrupt discontinuation of levothyroxine
Hypothermic environmental exposure
Pathophysiology
Profound thyroid hormone deficiency reduces metabolic rate, cardiac output, thermogenesis, and respiratory drive. CNS depression, hypoventilation with CO2 retention, hypoglycemia, hyponatremia (impaired free water excretion), and decreased drug metabolism produce a self-perpetuating spiral.
Clinical presentation
Symptoms
Progressive lethargy, somnolence, confusion, eventually obtundation
Cold intolerance, prior hypothyroid symptoms (constipation, weight gain, fatigue)
Family or caregiver report of stopped levothyroxine
Signs / physical exam
Hypothermia (often <35°C; may mask infectious fever)
Dry coarse skin, sparse hair, delayed deep tendon reflex relaxation
Goiter or thyroidectomy scar; hypoactive bowel sounds, ileus
Classic findings
Elderly woman in winter found obtunded with hypothermia, bradycardia, hyponatremia, hypoglycemia, and a thyroidectomy scar or prior levothyroxine prescription.
Differential diagnosis
Sepsis — Common precipitant — infection may be the trigger; obtain cultures and treat empirically
Hypothermia from environmental exposure — May coexist; thyroid testing in any unexplained hypothermia
Adrenal crisis — Often coexists; treat with stress-dose steroids BEFORE thyroid hormone
CT head if focal neuro deficit, fall, or anticoagulated
Echocardiogram if pericardial effusion suspected
Diagnostic algorithm
flowchart TD
A[Obtunded elderly patient<br/>+ hypothermia + bradycardia] --> B[Suspect myxedema coma<br/>± precipitant infection]
B --> C[Send TSH/free T4, cortisol,<br/>cultures, ABG, lactate, BMP]
C --> D[ABCs: intubate if needed<br/>Passive rewarm only]
D --> E[Hydrocortisone 100 mg IV q8h<br/>FIRST]
E --> F[Levothyroxine 200-400 mcg IV load<br/>then 50-100 mcg IV daily]
F --> G[Treat precipitant<br/>empiric antibiotics]
G --> H[ICU monitoring<br/>correct Na slowly, glucose, fluids]
H --> I{Inadequate response?}
I -->|Yes| J[Consider IV T3<br/>(liothyronine)]
I -->|No| K[Transition to PO levothyroxine<br/>when stable]
Myxedema coma — sequenced resuscitation (steroids before thyroid hormone).
Treatment
First-line
ABCs — intubation and mechanical ventilation if respiratory failure; passive rewarming (active rewarming can cause vasodilation and shock)
Stress-dose glucocorticoid FIRST — hydrocortisone 100 mg IV q8h until adrenal insufficiency excluded (giving thyroid hormone alone in unrecognized adrenal failure precipitates adrenal crisis)
Thyroid hormone replacement — levothyroxine 200-400 mcg IV LOAD, then 50-100 mcg IV daily; some experts add liothyronine (T3) 5-20 mcg IV load then 2.5-10 mcg q8h (cautious in cardiac disease)
Identify and aggressively treat precipitant — empiric broad-spectrum antibiotics until infection excluded
Supportive care: IV fluids cautiously (risk of pulmonary edema), correct hyponatremia slowly (avoid osmotic demyelination), glucose for hypoglycemia, avoid sedatives, ICU monitoring
Cerebral pontine myelinolysis from rapid correction of hyponatremia
PANCE pearls
Hydrocortisone BEFORE levothyroxine — always. Coexisting adrenal insufficiency is common and giving thyroid hormone first can precipitate adrenal crisis.
Look for the precipitant — infection (pneumonia, UTI), cold exposure, MI, stroke, or sedative use. Treating only the thyroid will not save the patient.
Passive rewarming only — active rewarming causes peripheral vasodilation and shock in these patients.
Sodium correction must be slow (<8-10 mEq/L per 24 h) to avoid osmotic demyelination.
Hypothermia in an obtunded elderly woman = check TSH while you check the cultures.
References
ATA 2014 — Guidelines for the Treatment of Hypothyroidism — Myxedema Coma section (Jonklaas et al., Thyroid 2014)
Mathew & Aronow 2011 — Myxedema Coma: A New Look into an Old Crisis (Mathew et al., J Thyroid Res 2011)
Wartofsky 2006 — Myxedema Coma (Wartofsky, Endocrinol Metab Clin North Am 2006)
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